Sitka waterproof breathable outer layers are originally treated with a Durable Water Repellant finish (DWR), which keeps the outer fabric from becoming saturated so that the breathable barrier can do its job. This coating needs to be replenished once per season, or more often if the piece gets a lot of use or washing. If water is no longer beading up on your shell, it's time to retreat it. Make sure to use a spray on our softshell pieces, and a wash-in for 2.5 layer garments, like the Downpour series. Additionally, don't hesitate to treat your Mountain Pants with a DWR spray and watch the water bead off.